Disclosed in embodiments herein are methods and apparatuses relating to an image forming machine, and more particularly, to determining the location of one or more biased transfer rolls relative to associated photoreceptors in a printer.
A typical electrophotographic, or xerographic, printing machine employs a photoreceptor, that is charged to a substantially uniform potential so as to sensitize a photoconductive surface thereof. The charged portion of the photoreceptor is exposed to a light image of an original document being reproduced. Exposure of the charged photoreceptor selectively dissipates the charge thereon in the irradiated areas to record an electrostatic latent image on the photoreceptor corresponding to the image contained within the original document. After the electrostatic latent image is recorded on the photoreceptor, the latent image is developed by bringing a developer material into contact therewith. Generally, the electrostatic latent image is developed with dry developer material, referred to as toner, comprising toner particles which are attracted to the latent image, forming a visible toner image on the photoconductive surface.
The toner image can then be transferred to an intermediate transfer surface at a biased transfer roll image transfer nip formed by an electrically biased transfer roll pressing the intermediate transfer surface against the photoreceptor. This serves to effect combined electrostatic and pressure transfer of toner images from the photoreceptor to the intermediate transfer surface. A high voltage power supply provides an electrical bias of a suitable magnitude and polarity so as to electrostatically attract the toner particles from the photoreceptor to the intermediate transfer surface to form the toner image on the intermediate transfer surface. Multiple toner images, each corresponding to a different color separation, can be transferred to the intermediate transfer surface to form a multi-color toner image. The toner image is then typically transferred to a substrate, such as paper and the like, to form a printed image.
The biased transfer roll can be moved away from the intermediate transfer surface, for various printing and non-printing conditions, and thus, it is desirable to determine the location of the biased transfer roll so as to enable image transfer, when so desired. Typically, optical sensors are used for this purpose. However, these sensors add additional costs and complexity to the printer.
Biased transfer roll assembly resistivity measurement routines have been used to determine various properties of the biased transfer roll, intermediate transfer surface, photoreceptor, and/or biased transfer roll image transfer nip. It is desirable to utilize biased transfer roll assembly resistivity measurement for determining the location of the biased transfer roll with respect to the image transfer surface and photoreceptor.